Flexible displays including rollable displays are expected to become more common place. Basically, flexible or rollable displays may be manufactured using a variety of display elements, e.g. Liquid Crystal Display (LCD) elements or Organic Light Emitting Display (OLED) elements, deposited on or sandwiched between flexible substrates, e.g. polymer substrates. Light emitting polymers offer various advantages such as excellent viewing angle and contrast, as well as low power consumption. Flexible passive matrix monochrome organic light emitting displays (OLEDs) have been demonstrated by U.S. and Far East companies, such as Pioneer, Dai Nippon, UDC, and DuPont Displays.
Generally, an OLED comprises an organic display element which is deposited on a base glass substrate and covered by an exit substrate. One of the critical issues for Organic Light Emitting Devices (OLEDs) is their lifetimes, which is largely limited by the degradation of the organic light emitting material induced by water and oxygen permeating into the display. Other displays and display effects are sensitive to water (and/or oxygen). For this reason, significant attention is paid to encapsulate the display appropriately. In flat panel displays, for example, appropriate encapsulation is achieved dominantly with the glass substrates. For flexible/rollable display applications, thin brittle layers are applied as permeation barrier, either directly on the display devices or parts thereof (thin film packaging) or on the (polymer) carrier substrates.
In addition to tightly encapsulating the display element(s), in order to provide for a fluid (gas or liquid) tight sealed environment, the front and back substrates are joined together by a seal(s) impermeable to water and/or oxygen. Furthermore, the displays are usually assembled in inert gas conditions, in order to eliminate any contamination from being contained in the display. However, there is always a risk that some trace amounts of oxygen or water remain in the display cell and/or the seals are not impermeable enough to moisture and gas. Therefore, packaging of polyLED devices deposited on glass currently involves gluing a rigid lid with getter on the glass substrate, which absorbs excess water and or gaseous substances in the display. However, even with the use of getter, there is still a need for displays that are highly impermeable and well sealed from the environment, such as high or low humidity and temperature conditions, as well as sealed to keep out oxygen, where humidity and oxygen tend to degrade the displays and reduce their useful lifetimes. Accordingly, there is a need for better displays or display cells which are better sealed and protected against the environment or exchange of fluids.